Noble Metal Nanoparticles, A Process For Preparing These And Their Use - Patent 8071259

Description: INTRODUCTION AND BACKGROUND The present invention provides noble metal-containing nanoparticles for producing membrane electrode assemblies (MEAs) for fuel cells, in particular for low temperature fuel cells, for example polymer electrolyte membrane fuel cells (PEM fuelcells) and direct methanol fuel cells (DMFC). New types of colloidal solutions which contain the noble metal alone or in association with other metals are described, wherein the metals are in the form of nanoparticles embedded in a temporary stabilizer. The nanoparticles are used to produce electrocatalysts and catalysed components for fuel cells. Using these nanoparticles, catalyzed ionomer membranes, catalyzed gas diffusion electrodes (so-called "backings") and membrane electrode assemblies can beproduced. Fuel cells convert a fuel and an oxidizing agent which are spatially separated from each other at two electrodes into electricity, heat and water. Hydrogen or a hydrogen-rich gas may be used as the fuel, and oxygen or air as the oxidizingagent. The process of energy conversion in the fuel cell is characterized by a particularly high efficiency. For this reason, fuel cells in combination with electric motors are becoming more and more important as an alternative to traditional internalcombustion engines. The PEM fuel cell is suitable for use as an energy converter in motor vehicles because of its compact structure, its power density and its high efficiency. The PEM fuel cell consists of a stacked arrangement ("stack") of membrane electrode assemblies (MEAs), between which are arranged bipolar plates for supplying gas and conducting electricity. A membrane electrode assembly consists of a solidpolymer electrolyte membrane, both sides of which are provided with reaction layers which contain catalysts. One of the reaction layers is designed as an anode for the oxidation of hydrogen and the second reaction layer is designed as a cathode for thereduction of oxygen. On these reaction layers are